1. Field of the Invention
This invention relates to the field of gas-propelled projectiles. More specifically, the invention comprises a marker flare projectile having an improved delay column ignition system
2. Description of the Related Art
Although the present invention can be configured to operate from a variety of different launchers, it was primarily developed to be fired from launchers adapted to fire 40 mm grenades (such as the U.S. Army's M433). The invention incorporates elements from a prior design reduced to practice by the same inventor. The prior design is disclosed and claimed in U.S. Pat. No. 7,004,074 to Van Stratum (2006), which is hereby expressly incorporated by reference.
Gas-propelled projectiles typically use solid propellant encapsulated in a cartridge case. A projectile is seated in the open mouth of the cartridge case. Ignition of the propellant is provided by percussive or electrical means. The burning propellant generates pressurized gas which forces the projectile out of the mouth of the case and then typically through a barrel bore.
This type of system is typically used to launch 40 mm grenades. The same approach can be used to launch other types of projectiles, however. An example of such a projectile is a marker flare. A marker flare projectile has a mass which is similar to that of a grenade round. Thus, the propulsion system developed for use with grenade rounds can be used to launch a marker flare. The incorporated U.S. Pat. No. 7,004,074 illustrates and describes an effective approach to the problem of launching large masses at low velocities. The '074 invention uses a high-pressure cartridge embedded within a low-pressure larger cartridge. A burst cup metering system is used to meter propellant gases from the high pressure cartridge into the low pressure cartridge, thereby accelerating the projectile in a smooth and controlled fashion. This approach helps to reduce the peak recoil loads experienced by a user. The high pressure found within the high pressure cartridge also ensures the reliable ignition and combustion of the propellant it contains.
The burst cup approach results in hot metered gases exiting the high pressure case in the direction of the mouth of the low pressure case. The present invention makes use of this phenomenon. In addition to propelling the marker flare down the bore of the firing weapon, the hot gases exiting the high pressure case are used to ignite a delay column in the aft end of the marker flare round.